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Oil in early Northstars?


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Please read Adallaks post about oil on 4.1/4.5/4.9 L engines before reading this.

What about the Northstar engines? On the pre-roller ones (before 2000 I believe?) there shouldn´t be any need for high rates of ZDP since there is no distributor, oil pump gearing, rocker arms etc. The only place in real need for ZDP protection should be the lifter surfaces.

My question of course is if we (the early Northstar owners) should use a diesel oil too?

Here is the original post from Adallak (quoting Bbob)

"The Rotella/Delvac/Delo diesels oils are "better" because of the higher concentration of the ANTI-WEAR additive ZDP.

Normal "gasoline engine" oil on the shelf (with the ILSAC star burst label on it saying "for gasoline engines") has lower levels of the anti-wear additive and it also has quite a bit of friction reducer additives...i..e...fuel economy improving additives.

The friction modifiers don't really hurt anything but the lack of high levels of ZDP is not good for older engines like the 4.9 with distributor drive gears which are heavily loaded. The distributor drive gear in the 4.9 engine is what needs the extra anti-wear ZDP to live.

The thicker viscosity isn't really required or necessarily "better" but it won't hurt the 4.1/4.5/4.9 engine at all. You might loose a little bit of cranking speed due to the thicker oil in the winter if you live way up north where it gets to -20 and below...otherwise, it won't hurt a thing.

Generically speaking, as an engine ages and miles pile up and some wear occurs bearing clearnaces open up slightly and the slightly thicker oil helps compensate for that, especially on the 4.9 which can often have the main bearing thump from the front main bearing with high miles.

The added ZDP is better for all engines, not just the 4.9 or pushrod engines. You have to look at the specific engine design to see if it really needs the added wear protection. The bad thing about ZDP (which contains zinc and phosphorus) is that it does poison the catalytic converter over time. Phosphorus in particular can reduce the efficiency of the cat so modern oils tend to have less and less ZDP in them to reduce the effect on the cat. As a result, modern engines are designed to run with lower and lower levels of wear protection...i.e..roller rockers, roller lifters, gerotor oil pumps, crank driven oil pumps, etc. The amount of ZDP in the oil is deliberaterly reduced and controlled in the ILSAC starburst "gasoline engine" oils to reduce the catalyst contamination. On an individual basis on one car the ZDP doesn't really affect the cat that much even over 100K but on the whole vehicle fleet (millions of cars) it does have a little effect on emissions so the reduction in ZDP is more for the common good than anything. On older engines, designed to run with oil with more anti-wear protection the new oils are not the best protection. The Rotella/Delo/Delvac is NOT rated by ILSAC for "gasoline engines" so it has much more ZDP in it since it is purposefully blended for "diesel engines" but you can use it in your gas engine with no problem.

The distributor gear drives the distributor AND the oil pump. The distributor doesn't require much force but the oil pump requires a lot of load which is what can wear the distributor gear out over time without adequate wear protection. Most cam-in-block...i.e pushrod...engines are like that, they drive the distributor and the oil pump off the cam shaft distributor gear. You are also on the right track with the gear design. A right angle drive gear is heavily loaded because there is a lot of sliding contact on the gear teeth so as the load goes up from the oil pump the distributor gear loading is increased dramatically. The distributor gear relies on the anti-wear additives in the oil to live. Same with the sliding bearing rocker arms in the 4.1/4.5/4.9. More modern pushrod engines have the oil pump on the crankshaft itself, a gerotor oil pump gear instead of spur gears, roller lifters and roller rocker arms.....all to reduce friction and reduce the engines dependency on ZDP depleted oil. This is also good in that it allows modern engines to go much further on oil changes since the oil is not depleted nearly as much and the engine is fine with the depleted oil that didn't have much ZDP to begin with. If you want more insurance against wear, though, feel free to use the Rotella/Delo/Delvac oils.

The diesel Rotella/Delvac/Delo oils are available in weights other than 15W40 (such as 10W30) but they can be hard to find as most of the class 8 diesels that the oil is specifically blended for are set up to use 15W40. Modern 15W40 oils do not have the poor viscosity improvers of past generation oils so they are fine to use. Plus, modern 15W40 oils that meet the diesel specs and the API SM performance specs have a lot of synthetic content and synthetic viscosity improvers so they are not a concern compared to the 10W40 and 15W40 oils of 20 years ago which were not desireable.

There are many factors involving the weight of the oil used in an engine including the operating temperature of the engine/oil, how the engine is clearanced when it is designed/built, what features are in the engine such as roller followers, etc.

Generally speaking I would never recommend any heavier oil than 40 weight in a passenger car engine. There are many caveats and nits to pick with that but there is really no reason to increase the oil viscosity beyond what the manufacturer recommends.

Increasing the viscosity of the oil does not necessarily lead to less wear. It can lead to more wear when the engine is cold if the oil cannot flow well. It can overload the distributor gear as mentioned if the heavy oil cannot be pumped when the engine is cold and is revved up too high. Too thick an oil can cause oil filters to blow off when the engine is cold and revved up due to excessive oil pressure.

On the other hand, air cooled motorcycle engines that are run hard will often use 50 weight oil or heavier because of the clearances in the engine opening up due to the high heat and the oil thinning excessively due to the high oil temps often seen with air cooled engines.

Understand that multivis oils such as 10W40 are basically 10 weight oil base stock with a viscosity improver package added to "thicken" the oil as it heats up so that it is the equivalent of hot 40 weight when hot. The viscosity improvers are long chain polymers that coil up when cold and stretch out when hot thus improving the viscosity. The bad thing is that the viscosity improvers, if not of very high quality, can break down in high heat areas and cause severe deposit build up that sticks rings in the piston ring grooves. This was a huge problem with multivis oils back in the late 70's and early/mid 80's with the SE and SF oils of that era. Oils with large viscosity spreads (such as 10W40) require large percentages of viscosity improvers which made them particularily bad for deposits back in the old days. That is why 10W40 oils were not recommended in many applications, why diesels never recommended multi-vis oils at all until recently and why 10W40 oils are really not recommended nor particularily desireable even today.

The viscosity improvers of today in the SL and SM rated oils are pretty much all synthetic and do not cause deposit formation problems anymore. Even so, mulit vis oils that meet the highest diesel performance specs are of the 15W40 variety which require less VI percentage than a 10W40 would....i.e..it takes less VI to make a base 15 weight oil the equivalent of a hot 40 weight than a base 10 weight oil.

In any case, it doesn't hurt much to increase the oil viscosity a little in most cases but the best approach is to use the recommended oil viscosity for the engine and not try to second guess the engineers that developed the engine. Most current production engines are recommended for 10W30 and lately 5W30 for improved fuel economy. The engines are designed for that and substituting thicker oil will not help durability at all and it would definitely hurt the fuel economy.

In the winter, cold cranking speed is governed by the oil viscosity. If you were to use 50 weight oil in very cold weather the engine would never start due to the fact that it would likely barely crank over. In cold weather 5W30 and 0W30 oils are common for cranking purposes."

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Please read Adallaks post about oil on 4.1/4.5/4.9 L engines before reading this.

What about the Northstar engines? On the pre-roller ones (before 2000 I believe?) there shouldn´t be any need for high rates of ZDP since there is no distributor, oil pump gearing, rocker arms etc. The only place in real need for ZDP protection should be the lifter surfaces.

My question of course is if we (the early Northstar owners) should use a diesel oil too?

To my recollection, Bbob did not recommend using diesel oil in the Northstar; however, he did say that older engines such as the old 350, which have pushrod lifters could use diesel engine oil of appropriate weight and even mentioned they would provide excellent protection for these older engines. As far as the Northstar, he said using the recommended weight oil is best. I also believe he mentioned that oils advertised for use in high mileage engines simply have more ZDP. While these high mileage oils may not have the same amount of ZDP as in diesel oils, it may be the better way to go if you want more ZDP protection.

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I´ve found this.

Quite interresting stuff about how the OLM works and great info about oils in general, the words are from the guru of course :rolleyes:

It really drives me crazy to se all those better knowing people with no real experience throw out stupid anouncements and badmouthing Cadillac and GM all the time, but otherwise its a good post.

Seems like it is ok to take whatever 10W-30 oil (even with lower ZDP) in our Northstars.

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PS (I saw Sweden....from Denmark )

Well then you should have come by for a cup of coffee! I can see Copenhagen (or at least the Öresundsbron) from where I live when the weather is good, but it always seems to rain here in Lund.

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Seems like it is ok to take whatever 10W-30 oil (even with lower ZDP) in our Northstars.

From my recollection, he said it’s best to use quality oils with a proven track record. I don't know if you remember the Guru discussing how oils are manufactured, however, from what I remember, the brand name oils are generally manufactured from the same base oil stock, then additives such as (ZDP, etc.) are mixed according particular brand specifications. Some brands contain better additive packages and thus can provide better overall protection, especially when changes occur at 5-12,000 mile intervals in accordance with the Oil Life Indicator. He also mentioned that base oil stocks are not the same, as some are of better quality than others. Thus, the less quality oils such as store brand oils might be manufactured from lower quality base oil stock.

He didn't say just throw in any oil you want because it’s all the same. Actually, he mentioned his choice of oil, however, I think it's not important to say which because there are several high quality oils on the market which will provide optimum engine protection. I've used Mobile, Quaker State, Pennzoil, Castrol, Valvaline, and a couple of others. Again, he said it's best to use the recommended oil called for by GM, however, to paraphrase, he said the type of oil, when, where, and why, is not an exact science. Nevertheless, after reading his posts at the link provided it's clear that he cautions about trying to out-expert engineers when it comes to choosing which oil is best or adequate enough, as exemplified below:

The factory recommended lubricants are correct. They have been tested and validated. If you chose to use some other recommendation or other product YOU are doing the testing and validation. If you are comfortable with that, fine, but understand that it is your responsibility, not the factory, to test and accept the results...good or bad. . . . .The OEM recommendations for the unit as delivered are the best and correct for what the vehicle was intended for and certified for. Period. Follow them for best results.

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Hi MAC.

Perhaps I should clarify my statement above.

I mean that it seems to be ok to use any 10W-30 oil with a service grade higher than the SG grade that was to be met -93 when my STS was new. Reading about today's oils being in service grade SM should be ok since every new step on the scale according to the API exceeds the recommendations of the former grade, including wear protection.

Surely the ZDP rate is decreased for the reasons mentioned i Bbobs posts but there has to be other wear protectors to substitute the loss of them (at least according to a statement from a tech working at Royal Purple).

I'm not trying to do my own testing :lol:

I´m just trying to figure out what oil I should use since the grade SG isn´t available any more.

What worries me is that Bbob says that the ZPD levels has been decreased, but it shouldn´t be a problem if it´s true that an oil of a higher API grade must at least exceed the prior grade reguarding wear protection etc.

Does anyone have any insight in this? I sure wish the guru was still around.

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I don't think it really matters what oil you use. As long as you change it as required, it is not going to self destruct.

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I mean that it seems to be ok to use any 10W-30 oil with a service grade higher than the SG grade that was to be met -93 when my STS was new. Reading about today's oils being in service grade SM should be ok since every new step on the scale according to the API exceeds the recommendations of the former grade, including wear protection.

You would be correct.

Look for the "starburst symbol" and the API service-rating label to verify it is the recommended oil for your Eldorado.

I'm looking at a quart of 10W-30 Quaker State Peak Performance oil and the label says: Meets or exceeds requirements of ILSAC GF-4, GF-3, API SM and previous API standards. Some non-brand oils will not meet the newest ILSAC standards but will meet previous standards. As long as the oil meets standards called for by GM for your engine you will be fine. However, bear in mind that all oil is not the same depending on base stock and additive package. Accordingly, I would shy away from store brand oils. As the Guru pointed out, store brand and the less expensive oils will generally have inferior additive packages in comparison to brand name oils.

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